Central heating system with no thermostat

[Dave Baker]

Can't find a thermostat anywhere in my bungalow which puzzles me. The heating system is only about 20 years old (as is the house), oil fired boiler, TRVs on all the rads except the one in the hall. Since moving in 18 months ago I've managed by closing the flow valve on the hall rad so that's permanently off, plus turning down the TRVs in all the rooms I don't use to frost setting and letting the other TRVs control the temp I actually want in the kitchen, shower room and my bedroom which they do quite well.

However the boiler cycles on and off pretty rapidly (every five to ten minutes or so) as the temperature of the water in it triggers its own internal stat and then even if the main rooms don't need more heat it still heats the water in all the pipework under the floor, even to all the bypass pipework to the rads at the far end of the house that are closed off, and I suspect I'm wasting a lot of oil keeping all those pipes hot every few minutes whereas the hysterisis in a room stat would perhaps prevent the boiler cycling anything like as often.

Maybe I'm fussing over nothing as my oil usage is quite low but I've never had a house without a room stat before.

Comments, suggestions?

[Adrian]

Not an entirely unusual situation.

Adding a room stat shouldn't be difficult. How far away's the boiler from a potential sensible position?

[The Natural Philosopher]

fit a radiostat

[Roger Mills]

It's certainly desirable to have stat which turns everything off when the demands are satisfied - and a legal requirement for more recently installed systems which need to comply with the latest regs.

It's usually quite easy to fit a room stat. You've probably got a wiring centre somewhere, where all the connections for the boiler, pump, zone valves, etc. are concentrated. Somewhere in there, you're likely to find a link bridging two terminals to which a stat could be connected. It's as easy as removing the link and wiring a stat in its place.

A wired stat is the easiest option (electrically) as long as the desired position is not too far away from the wiring centre and/or you can easily install and hide a cable between the two.

Otherwise use a wireless stat. The base unit which does the actual switching can be very close to the wiring centre, and the remote part which sends radio signals to control the switching can be anywhere you like (within reason!). The base unit takes a bit more wiring in than a wired stat because it needs a permanent supply in addition to the feed which it's switching.

I'm assuming in both cases that you'll use a digital programmable stat rather than an old fashioned mechanical stat. You can then leave the original programmer permanently on, and use the stat to do the timing - with the option of having different target temperatures at different times of day.

[Bill Wright]

They're very good. Solved my problem. I mean the problem I had with the central heating, not one where I suddenly undress completely at funerals.

Bill

[Tim+]

You too? Thought it was just me...

Tim

[Peter Crosland]

It is more widespread than you think.

[Michael Chare]

I use a 2 channel programmable thermostat with my oil fired boiler. The programmer itself is nearly 10 years old.

One channel controls the hot water (off and on twice per day)

The other channel varies the temperature up to six times per day.

I got rid of some TRVs, party because they broke, and anyway they try to maintain a constant temperature which is not what I want.

The programmer I have uses a remote wired sensor which is located in the sitting room. The programmer itself is close to the boiler.

One of its benefits is that it is actually very good at maintaining the desired temperature by cycling the boiler off/on to produce the desired amount of heat. Much better than the previous mechanical thermostat which had a large hysteresis.

[John Rumm]

For the OP, all the common wiring layouts are shown here and in the downloadable docs at the end:

[PeterC]

Aye - otherwise the funeral is more than you can bare.

[Dave Baker]

If it isn't actually causing me any boiler inefficiency then I'm ok with it.

The boiler is in the utility room next to the kitchen where I spend most of my time so just a few feet away.

[John Rumm]

It will be on two counts - excessive cycling (not the demon it once was if you have pump overrun and a low water content HE), and running unnecessarily when the house is warm enough.

I guess the question was more of the from, how difficult would it be to get a cable from the boiler to a decent position for a thermostat? If easy, then do it, if not, then get a wireless stat.

[Cursitor Doom]

I've got no thermostat here either. I plan to fit one when I get time, though. I've got along reasonably well over the last 2 years with TRVs on the rads and by turning the main dial on the boiler itself up and down as required, although my friendly heating engineer tells me it puts extra strain on the boiler for some reason. :-/

[John Rumm]

it means it spends lots of time running when it could be resting ;-)

[Grimly Curmudgeon]

Used to be fairly common for builders and so-called heating engineers to fit a 'stat-less system, relying on the boilerstat to do crude control. Why on earth they bothered to be so fecking slipshod and slapdash to save the cost of a roomstat and tuppence worth of cable, defeats me.

Easy to upgrade it, of course.

[Jim S]

My Worcester was like that initially ie controlled by the water returning to the boiler. I had a wireless stat fitted, but not fixed to the wall so I can have it in the room I'm in. However I'm not sure it make an awful lot of difference. I believe new systems have to have room thermostats by law.

[John Rumm]

Cos it cost less in parts and was quicker to install, and they were not going to be paying for the fuel.

[John Rumm]

They have to have an "interlock" of some form - it does not actually specify a room stat, although that is the normal way of achieving the requirement.

[chris French]

I'm still bemused by the roomstat that was fited in this house when we moved in, cable back to the CH wiring, but not connected up.

Their gas bills were enormous by the sound of it (as opposed to just very large now....) when we moved, and I went to move the supply over to our then current supplier they wouldn't put us on the same tarrif as the gas consumption record showed it was to high - over 88000 kWH a year or somethign like late

[John Rumm]

I had a similar problem when I tried to change providers after moving - the web quotes refused to accept that the figures could be right! ;-)

(Had to tell them we cooked on gas as well to get past the sanity checks)